Rainwater Harvesting

Rainwater cropping or harvesting is the capture of rain water from rooftops, diverted by a system of gutters, pipes and filters into storage for later use. This rainwater can easily be used for non-potable uses such as irrigation, cooling towers, (some) washing purposes, ornamental fountain filling, and toilet flushing (U.S. Department of Energy, n.d.). With further retrofitting of any basic rain harvesting system to include sufficient filtration and disinfection, this water can also reach potable standards and supplement a community’s freshwater supply for drinking, cooking, showering, and more. The available amount of water that can potentially be collected through rainwater harvesting depends on the amount of rainfall in an area along with the size of the surface area(s) the system is collecting from. The U.S. water collection formula is:

Catchment area (ft^2) x Rainfall (inches) x 0.623 (conversion rate) = Gallons of water

In the U.S. the average single-family roof size is 1,700 square feet (Roof Keen, 2021). According to the Southwest Florida Water Management District, the region receives and average of 7.8 inches of rain per month during the rainy season (4 months) and an average of 2.7 inches during the dry season (8 months) (McBride, 2022). This means that during rainy season the Southwest Florida residents could be collecting about 8,261 gallons of rain per month (per average single-family home) and 2,860 gallons per month during the dry season. Annually this amounts to 55,924 gallons of rainwater per average single-family home. This does not include rainwater that could be captured from commercial or municipal buildings such as schools, hospitals, office buildings, hotels, condo/apartment buildings, restaurants, etc.As far as storage goes, each system can include one or multiple barrels or tanks (of various sizes) for the catchment and storage of rainwater. The only requirement is that the storage unit be opaque or non-translucent so that algae does not begin to grow inside due to light exposure (SWFWMD, n.d.).

Rainwater harvesting systems are an important green infrastructure to implement in any community due to its positive environmental impacts. These include but are not limited to, reduced energy use (from municipal water distribution), reduces greenhouse gas emissions (from energy use), reduced storm water runoff pollution, reduced storm water run-off (causing flooding and heat-island effects), and increased water security in water scarce regions (De Sa Silva et al., 2021). As you can see rain harvesting is a great supplementary tool for hindering further climate change and adapting to the inevitable present and future effects of it. Long-term, the sustainability of rainwater harvesting also adds to, “better sanitary conditions and consequent improvement in public health, [and] in guaranteeing water for the [further] development of economic activities, such as agriculture” (De Sa Silva et al., 2021).

Public opinion and perception on rainwater harvesting is generally positive however there are some challenges that get in the way of more people implementing them into their dwellings. The main barrier is the perceived cost of installing the system. People have low confidence in the water savings and do not like the idea of losing money in the short term (Alim et al., 2019). Additionally, people seem to get overwhelmed with the various forms of rain harvesting systems and which is best for them (size, actual savings, residential restrictions) and the inconvenience/complexity of the installment process itself (Alim et al., 2019). They also seem intimidated by the logistics and maintenance of the system once installed (Water Wise, n.d.). For the most part people seem more comfortable moving into a house or building with an already existing system, than having to get new one installed in their existing homes (Water Wise, n.d.). A lot of these concerns are valid, however misplaced due to conflicting or misinformation. “The more knowledge and understanding people have about how the systems function, the more accepting they are likely to be” (Water Wise, n.d.).

Ultimately, the benefits of rainwater harvesting outweigh the drawbacks. The pros include: long-term water savings, reduction in municipal water use (relieves demand, and energy use), has positive (at worst very low) environmental impact, long-term sustainability for economy and public health, relatively inexpensive and low maintenance (contrary to perception), potential for tax incentives and/or government funding, and is easily replicable for other sites. The cons are based in the perception of a complex system with complex installation and maintenance. Additionally, the low or negative return on investment in the short term can turn people away from committing to such a lifestyle change. Too many potential options of systems can also overwhelm people who are knew to the concept and rather not go through the hassle at the end of the day. Alas, there is not enough research, or conflicting research of sanitation aspects when using the water for potable purposes. This may add to governments’ slow reaction to implementing incentives and funding to large-scale rainwater harvesting system retrofitting initiatives. Lastly, a great benefit to this freshwater alternative is its compatibility with reclaimed wastewater and the use of greywater systems.

References

Alim, M. A., Rahman, A., Tao, Z., Samali, B., Khan, M. M., & Shirin, S. (2020). Suitability of roof harvested rainwater for potential potable water production: A scoping review. Journal of Cleaner Production, 248. https://doi.org/10.1016/j.jclepro.2019.119226

De Sá Silva, A. C., Bimbato, A. M., Balestieri, J. A., & Vilanova, M. R. (2022). Exploring environmental, economic and social aspects of rainwater harvesting systems: A review. Sustainable Cities and Society, 76. https://doi.org/10.1016/j.scs.2021.103475

McBride, T. (2022, March). Hydrologic conditions. Southwest Florida Water Management District. Retrieved January 4, 2023, from https://www.swfwmd.state.fl.us/about/newsroom/hydrologic-conditions-0

RoofKeen. (2022, January 22). How many square feet is the average house roof? Retrieved January 4, 2023, from https://roofkeen.com/how-many-square-feet-is-the-average-house-roof/

SWFWMD (Southwest Florida Water Management District). (n.d.). Rain barrels. Retrieved January 4, 2023, from https://www.swfwmd.state.fl.us/residents/water-conservation/rain-barrels

U.S. Department of Energy. (n.d.). Water-efficient technology opportunity: Rainwater Harvesting Systems. Office of Energy Efficiency & Renewable Energy. Retrieved January 4, 2023, from https://www.energy.gov/eere/femp/water-efficient-technology-opportunity-rainwater-harvesting-systems#:~:text=Harvested%20rainwater%20can%20provide%20a,from%20rooftops%20for%20later%20use.